Ultrasound-guided biopsy of the cricoarytenoideus lateralis muscle: Technique and safety in horses

Summary Reasons for performing study Current diagnosis of recurrent laryngeal neuropathy (RLN) depends upon disease recognition in the clinically affected horse. Biopsy of the intrinsic laryngeal muscles may provide a method to identify the changes in fibre-type composition that occur in RLN before clinical signs become apparent. Objective To develop an ultrasound-guided biopsy technique of the left cricoarytenoideus lateralis muscle (CALM) and evaluate its efficacy and safety in vivo. Study design A longitudinal descriptive study. Methods Six standing horses underwent ultrasound-guided biopsy of the left CALM. Frozen muscle cores were obtained with a breast biopsy tool. Serial endoscopic, ultrasonographic and physical examinations before and for 8 weeks after the biopsy were assessed for iatrogenic trauma. Histologies of representative muscle core cross-sections were analysed for the total number of muscle fibres obtained with each biopsy. Results There were no immediate complications of the procedure and the left CALM was harvested in all instances. Biopsy samples had an average weight of 0.043 g (range = 0.023–0.077 g) and contained 3418 fibres in cross-section (range = 711–7143). Laryngeal endoscopic grade did not change significantly between prebiopsy and the end of the 8 week follow-up. The left CALM had significantly greater echogenicity than the right throughout the study (P<0.001), but there was no difference between the prebiopsy CALM echogenicity and that at completion of the study. Conclusions Ultrasound-guided biopsy of the left CALM is safe and well tolerated, providing a minimally invasive method to obtain muscle from healthy horses. This new technique may be applicable in research and clinical settings.